As we know, the epidermis is a fabric that covers the entire body of a plant, being considered the most external tissue of the plant. In this tissue, several structures are present, such as trichomes, hydatodes and stomata.
You stomata they are structures that, seen under a microscope, resemble small mouths, which is why they received this name, which comes from the Greek stoma, which means mouth. The main function of a stomata is to control the entry and exit of gases, so we can conclude that they are directly related to the performance of the process of photosynthesis.
The stomata are found mainly on leaves and stems, being absent from roots. These structures can be located only on one leaf surface or on both, and this is an important criterion for classifying the leaves. When a leaf has stomata on both sides, we say it is amphistomatic. When the stomata are present only on the underside of the leaf, we say that it is hypostomatic. When the stoma presents itself only in the upper region, we say that it is a leaf epistomatic.
A stomata has a very characteristic structure: it is made up of two cells, called a guard cells, which are around an opening called ostiole. This opening connects the outer medium with a space between the cells called the substomatic chamber.
Note the structure of a stoma
Guard cells play an important role in controlling the opening and closing of the stomata and, therefore, ensuring gas exchange. These cells differentiate according to the species analyzed, and they usually have kidney shape in eudicots and dumbbell shape (gym weights) in species monocots.
In some stomata, we also find the so-called subsidiary cells, which are around the guard cells. The quantity and arrangement of these cells are criteria for classifying a plant's stomata.
By Ma. Vanessa dos Santos
